Table of content

Iraqi journal of mechanical and material engineering

المجلة العراقية للهندسة الميكانيكية وهندسة المواد

ISSN: 20761819
Publisher: Babylon University
Faculty: Engineering
Language: Arabic and English

This journal is Open Access

About

Iraqi journal for mechanical and material engineering is a refereed scientific journal published quarterly by the engineering college/ university of Babylon. It deals with high quality researches in fields of mechanical and material engineering.

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Contact info

Journal E-mail:
j.mec_mat_eng@yahoo.com
Babylon university/Babylon/Iraq P.O.Box(4)
Tel:++96430245387.(1155)

Table of content: 2009 volume:9 issue:2

Article
EXERGOECONOMICS ANALYSIS OF COUNTER FLOW HEAT EXCHANGERS

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Abstract

The irreversibility minimization method of heat exchanger optimization is extended to include a term to account the energy of the material of construction of the heat exchanger. The method permits physically realistic optimization to be conducted with the resulting optimum designs providing conceptually beneficial guideposts, which do not change with time or location. Such optima are in contrast to the optima obtained by presently advocated methods, which on one hand indicate unrealistic infinite area of the heat exchangers, and on the other hand point to optima that may change dramatically with location and time. Accompanying exergetic efficiency expressions using the same type of material exergy term show physically more realistic values than the usual expressions.

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Article
THE INFLUENCE OF FRICTION FACTOR ON THE COMBINED CONVECTIVE AND RADIATIVE HEAT TRANSFER IN A RECTANGULAR DUCT WITH INTERIOR CIRCULAR CORE

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Abstract

The effect of friction factor on the steady state natural convective – radiative heat transfer in an inclined rectangular channel with concentric circular core is investigated from continuity, momentum and energy equations. These equations are normalized and solved using the Vorticity-Stream function and the Body Fitted Coordinates (B.F.C) methods. The finite difference approach with the Line Successive Over-Relaxation (LSOR) method is used to obtain all the computational results. The (B.F.C) method is used to generate the grid of the problem. A computer program (Fortran 90) is built to calculate the Nusselt number (Nu) and friction factor f in steady state flow for thermal boundary condition of constant wall temperature and for aspect ratio AR (0.55-1) and geometry ratio GR (0.1-0.9). The fluid Prandtl number is Pr = 0.7, Rayleigh number (0 ≤ Ra ≤ 104), Reynolds number (1 ≤ Re ≤ 2000), Optical Thickness (0 ≤ t ≤ 10), Conduction- Radiation parameter (0 ≤ N ≤ 100) and Inclination angle (0˚ ≤ λ ≤ 90˚). The results show reasonable representation to the relation between Nusselt number and friction factor with other parameters (AR, GR, and Re, Ra, λ, t and N). Generally, Nu will be increased with increasing Ra, t, N, λ, and Re. In the same time, fRe will be increased when Re and GR increase and AR decrease. The effect of radiation on the bulk temperature is concluded by correlation equations.


Article
TRENSENT HEAT TRANSFER IN CIRCULATING FLUIDIZED BED
انتقال الحرارة بالحالة غير المستقرة في الأبراج ذات الطبقات المميعة المدورة

Authors: Dr. Hafidh Hassan Mohammed
Pages: 160-172
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Abstract

The paper presents practical data from the experimental work on heat transfer between immersed heat transfer surface and Circulating Fluidized Bed (CFB) in special experimental rig with certain dimensions and with set of operation conditions at constant heat flux (120 W) supplied to the electrical heater. The fluidizing medium was air at different velocities ( 4 and 5.5 m/s)and two different size of sand particles were employed (161 and 257 µm), as well as , different initial bed heights were used in the experiments ( i.e, 18 and 31 cm). Heat transfer coefficients calculated instantaneously by instant temperature of bed and heater surface are found to increase with fluidized air velocity and with heat flux, but, they show an inverse dependence on particle size, and directly proportional with initial bed height which represents the bed density. The stabilization case depended strongly on fluidization density, where the required time to reach steady state case of heat exchange increase with increasing initial bed height as well as increasing the particle size. The experimental heat transfer coefficient data were correlated in terms of Nusselt number with other parameters. This correlation of the present study are assessed by comparing it with the available correlation in literature for the overall heat transfer coefficient. Comparison shows reasonable agreements in some results and large deviation in others. Also this correlation not to correspond with the experimental values in some conditions.

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Article
AN APPRAISAL OF EULER AND JOHNSON BUCKLING THEORIES UNDER DYNAMIC COMPRESSION BUCKLING LOADING .

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Abstract

This research presents an appraisal for Euler and Johnson theories based on experiment tests under compression dynamic buckling load. 20 specimens ( columns ) made from two materials, namely 1020 Hot Rolled and 5052 Aluminum alloy, are tested under compression dynamic buckling load. The following remarks can be concluded from the present work : 1- Euler ( for long columns ) and Johnson ( for short columns ) theories can be used to estimate the dynamic critical buckling load with design factor of 3 or more. 2- Initial deflection of column has an important effect on compression dynamic critical buckling load.


Article
Detection of Crack in a Simple Unswept Wing Using Free Vibration Analysis
الكشف عن الشق لجناح بسيط غير مرتد بأستخدام تحليل الأهتزاز الحر

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Abstract

The present research is concerned with an investigation of the vibration characteristics of a cracked wing structure. Finite element method has been used to formulate the free vibration analysis. Ansys v9.0 program as a mathematical tool was used in implementation the analysis and extract the results. Effect of several parameters such as (effect of crack ratio, crack location, and crack inclination angle) on the natural frequencies and mode shapes were studied. The results indicate that the natural frequencies are affected in the presence of a crack; but it doesn’t give an indication to the crack location. While, using mode shape is a powerful tool to detect the crack and its magnitude along the wing’s length. The crack inclination angle is investigated to show its effect on the crack identification where relatively little error may appear if crack angle wasn’t normal to the wing axis. Also the presence of the crack may cause to transform and exchange the modes between each other depending on the crack location and its magnitude.

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Article
STUDYING THE EFFECT OF A TRIANGLE PROTRUSIONS DIMENSIONS ON HEAT TRANSFER AND FLUID FLOW OVER A HEATED FIN INSIDE RECTANGULAR DUCT
دراسة تأثير أبعاد النتؤات المثلثية على انتقال الحرارة والجريان على زعنفة ساخنة داخل مجرى مستطيل الشكل

Authors: Dr. Ahmed Hashm Yousif
Pages: 198-212
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Abstract

A numerical study was carried out to investigate fluid flow and heat transfer over a heated fin (at constant heat flux ) with using a triangle protrusions with Reynolds number range (350 – 2000) and Pr=0.71. Different distance between the protrusions (b/H =0, 0.17, 0.33, 0.67, 1 ) with different height of protrusion (l/H =0.033, 0.067, 0.1 ) was used were (H) is the height of duct. The geometrical configuration of interest is similar to a single element of a plate- fin cross flow heat exchanger. The installation of protrusion is organized, in such way that increased the surface of fin and mixed the flow near the fin with main flow. A finite volume procedure was used to solve two dimensions conservation equations (mass, momentum and energy) with collocated grid. The results illustrate the essential significance of protrusion height and the distance between the protrusions base. Also, results show the heat transfer increasing with using protrusions as well as increasing pressure drop.

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Article
Corrosion Mechanism of Refractory Bricks Lining the Cement Kiln

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Abstract

Present work investigates causes of damage of two types of refractories, the magnesite 80% MgO and high alumina > 70% Al2O3 lining kiln of ordinary Portland cement at the burning and lower transition zones respectively. To estimate degree of penetration of cement clinker during kiln operation, chemical analysis was conducted for bricks after use for a limited period of time ,and also for clinker before and after burning to eliminate detrimental corrosive materials (like alkalis, sulfur, chlorine). Measurements of corrosion with time were reported and an experimental test was conducted to study the alkali attack on high alumina and its effect on the thermo-mechanical –chemical corrosion. The results showed that alkali attack on alumina brick is the main factor of its damage. The damage of magnesite brick refers to peeling of clinker coating during the cooling of the kiln as well as the immigration of chromites from hot to cold face decreasing the toughness of the brick.


Article
Characterization of petroleum fractions
خصائص القطفات النفطية

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Abstract

Petroleum streams produced from distillation of crude oil such as gasoline, kerosene, diesel fuel, fuel oil, etc. are complex mixtures of large numbers of hydrocarbon components, such fractions are generally characterized in terms of small petroleum cuts, or pseudocomponents, which are identified primarily by their boiling point and specific gravity due to their true boiling point curve (TBP), based on these two properties empirical correlations were derived to predict other components physical properties required for the process calculations. In the present paper empirical correlations was compared to other correlated equation and gives a good agreement. The proposed model is very interest for vapor-liquid equilibrium calculations of complex mixtures.

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Article
Studying the Flexural Characteristics of the Epoxy RENFORCED BY AL AND CU PARTICLES
دراسة خصائص الأنحناء للأيبوكسي المقوى بدقائق ِ (Al) و (Cu)

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Abstract

In this research the flexural characteristics of the composite beam made from epoxy reinforced by (Al) and (Cu) particles with different volume fraction (3%, 6%, 9%, 12%, and 15%) where studied. The results show that the modulus of elasticity, the flexural strength and maximum shear stress increase with increasing the volume fraction of the reinforced particles of (Al) and (Cu), while the deflection decreases with the increasing the volume fraction. And the results show that the reinforcement with Cu particles give the best results than the reinforcement with Al particles. The maximum values of the modulus of elasticity, flexural strength and maximum shear stress for the epoxy reinforced by Cu particles was (4600 MPa.) ,(1535 MPa.) and (18.1 MPa.) respectively at the volume fraction (Vf =15 %).

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Article
Study the effect of the some of the dominant effective parameters In the heat performance to evaporative air cooler
دراسة تاثير تغير بعض العوامل المؤثرة في الاداء الحراري لمبردة الهواء التبخيرية

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Abstract

This study included the effect of the some of the dominant effective parameters In the heat performance to evaporative air cooler, like flow rate of water that used as cooling medium in addition to the climatic conditions , besides study effect of treating heat exchanger surfaces by sawdust from wetted channels side, where in this study the design and installation of evaporative air cooler was carried out using completely outdoor air ( fresh air ) according to two stage evaporative cooling principle . The laboratory equipment was installed by designing and manufacturing a cross flow plate heat exchanger , where aluminum plates used for this purpose with dimensions ( 50 × 30 × 40 cm ) . The surfaces of heat exchanger were covered by sawdust from wetted channels side , to increase the percentage of wetting these surfaces and hence improve the performance and efficiency of air cooler . Water flow rate was varied from ( 144 L / hr ) to ( 1050 L / hr ) . Also effect of air dry bulb temperature was studied where varied from ( 30 oC ) to ( 50 oC ) , and ( 19.8 to 26.4 oC ) for the wet bulb temperature . The experimental results showed that the optimum flow rate of water that must be circulated in the cooling system was ( 450 L / hr ) , by using air at temperature ( 42 oC ) for dry bulb and ( 21.9 oC ) for wet bulb . The results were obtained at previously mentioned conditions concerning the cooling efficiency was ( 61.48 % ) , and the coefficient of performance ( 33.50 ) , and specific power consumption reaches ( 4.7 W. min / kg dry air ) .

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Article
The Effects of Wet Etching of Glass Fibers and Polyamide Fibers on The Bending and Impact Properties of The Resulting Composite Materials
تأثير التحفير الرطب لالياف الزجاج والياف البولي اميد على خواص الانحناء والصدم للمواد المركبة الناتجة

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Abstract

Improving the bonding strength can be achieved by surface treatment of fibers . Etching is one of the methods of this treatment , in this investigation wet etching of E-glass fibers and polyamide fibers carried out by using (H2O + NaOH) solution to get pits on their surface to increase the surface roughness . Group of tests was carried out to study the effect of this treatment on the mechanical (bending and impact) properties of a material composed of unsaturated polyester reinforced by (10 % wt) of etched glass fibers and Etched polyamide fibers . Also Calculation of the weight loss and executing of microscopic photo . The results show : - Increase of the bending strength of etched glass fibers reinforced composite materials with a maximum percentage of (301 %) compared with samples reinforced with untreated fibers . This maximum percentage was found when the fibers are treated at (25 oC) for (1 % NaOH) and (3 hr) . - Increase of the bending strength of etched polyamide fibers reinforced composite materials with a maximum percentage of (155 %) compared with samples reinforced with untreated fibers . This maximum percentage was found when the fibers are treated at (25 oC) for (1.5 % NaOH) and (3 hr) . - Increase of the impact strength of etched glass fibers reinforced composite materials with a maximum percentage of (270 %) compared with samples reinforced with untreated fibers . This maximum percentage was found when the fibers are treated at (25 oC) for (1 % NaOH) and (3 hr) . - Increase of the impact strength of etched polyamide fibers reinforced composite materials with a maximum percentage of (232 %) compared with samples reinforced with untreated fibers . This maximum percentage was found when the fibers are treated at (25 oC) for (0.5 % NaOH) and (5 hr) . - Increase of the weight loss of polyamide fibers than weigth loss of glass fibers .

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